Antonio Martinez, 21, is accused of taking what he thought was a car bomb to a military recruiting center outside Baltimore. When he tried to detonate it Wednesday morning, he was taken into custody.

The device was inert, given to Martinez by an undercover FBI agent. Holder said in a news conference Thursday that the tactics the FBI used in the sting are not entrapment.

On any number of occasions, the people who were arrested were given the opportunity to turn away from their stated desire to harm American citizens," Holder said. "The techniques we used, as I said, I think are legitimate. The way in which these techniques have been employed has been appropriate."

Martinez and his mother clashed over his increasingly radical views. He began calling himself Muhammad Hussain but never got around to legally changing his name.

Fed by Internet sermons and videos, the 21-year-old became obsessed with jihad, according to court documents and postings on his Facebook page.

His quick radicalization culminated in his arrest Wednesday on charges he tried to blow up a military recruitment center. The car bomb he is accused of trying to detonate was a fake provided by the FBI, which had been keeping tabs on him since October.

Martinez was born outside the United States to a Nicaraguan father and an African-American mother. Public records are unclear about when he moved to Maryland, although he attended Laurel High School in Prince George's County, a Washington suburb. The married, part-time construction worker had become a Muslim within the past two years, though authorities did not know why he was drawn to the religion.

His mother, who would not give her name, told The Associated Press outside her apartment Thursday morning that she tried to persuade her son not to convert. She said she was angered by his alleged actions.

"I'm embarrassed, and I tried to talk him out of being Muslim, period, because I'm a devout American, totally against what he started," the woman said. "But he got into it."

She would not say more, adding that she had yet to speak to her son's attorney. Court documents indicated that he told an FBI informant she was unhappy about how he had chosen to live his life.

On his Facebook page, Martinez describes himself as "just a yung brotha from the wrong side of the tracks who embraced Islam." Several of his posts criticize people who oppose the religion, and they are what led the informant to contact the FBI about him, documents show.

His brother-in-law, Kojo Ghana, tried to temper the strident messages Martinez posted. In response to his statement that "the reign of oppression is about to cease," Ghana wrote: "Until that day comes ... Help those who are in need of help, volunteer at a food bank, tutor, or something Constructive."

Reached through Facebook, Ghana referred questions to Martinez's public defender, Joseph Balter, who cautioned Wednesday against a rush to judgment in the case. Balter declined to comment further Thursday.

No one answered the door at the apartment building in northwest Baltimore that Martinez gave as his address in court, and a neighbor said she did not know him. Attempts to reach his wife at her home in Massachusetts were unsuccessful, but Martinez told the informant she understood his commitment to jihad.

Naheem Rafiq, the owner of a halal grocery store in Woodlawn, said Martinez had shopped in his store, but he had not seen him in months and did not really know him. A nearby mosque where Martinez reportedly prayed was empty when a reporter visited Thursday afternoon.

Martinez told a judge Wednesday that he did construction work. He had several scrapes with the law in his teenage years, and according to court documents, he believed he could not buy a gun because of his criminal record.

In 2006, when he was 16, he was arrested in the armed robbery of a Subway restaurant, according to a report from Montgomery County police. Although he was initially charged as an adult, a police report in a subsequent case indicated that he was placed into a program for juvenile offenders.

He was charged in 2007 with stealing a car _ those charges were dropped _ and in 2008, he pleaded guilty to misdemeanor theft and was given a suspended jail sentence, probation and a $500 fine. In that case, Martinez and another young man conspired to steal $160 from a grocery store cash register, according to a police report.

Before he became a Muslim, Martinez considered enlisting in the military, he told the FBI informant, and he picked the military recruitment center as a target because he had been inside.

He appears to have been exposed to radical Islam largely through the Internet. He referred to American-born radical cleric Anwar al-Awlaki, who has links to several alleged terrorists, as his "beloved sheikh," documents show. He also praised Omar Bakri Muhammad, the former leader of a radical group whose videos are widely available online.

"He wasn't very sophisticated," said Patrick Moran, the government's former top terrorism prosecutor, "but that's maybe what you would expect from a person who has come about his views via the Internet."

The FBI informant and undercover agent who communicated with Martinez gave him repeated opportunities to back out of his plan to bomb the recruitment center, documents show. But he insisted he was committed to the plot _ even after a Somali-born teenager was captured in Oregon in a similar phony bomb sting.

Given several chances to back out of the plot, Martinez declined.

"I am sacrificing so much for Allah," he told the FBI informant and an undercover agent in one of those conversations. "The path I have chosen is jihad."